How Solar- vehicle Ventilators Work

Due to their dependence on the sun, solar car ventilators do have a few weak points:

They often need direct sunlight to function, so they may not work on hot but cloudy days

Manufacturers warn that the devices won't work when mounted on tinted windows

Solar ventilators require you to crack open your car window, which could conceivably invite thieves to attempt breaking into the car

Luckily for eco-friendly drivers, some car manufacturers are already on the case. Owners of solar car ventilators have frequently complained that the devices don't work away from direct sunlight. In fact, parking in the shade or even with the solar panel facing away from the sun can render solar vents useless. To address this, some manufacturers now make solar vents that also plug into a car's 12-volt power receptacle. So, when available solar power is too weak to drive the fan's motor, the ventilator draws a small amount of electricity from your car's battery.

You've probably already started thinking about the money you could save by keeping your air conditioning off during the dog days of summer, but you should hold off on that thought for now. Solar-powered car vents are in no danger of replacing regular air conditioning anytime soon. Air conditioning uses highly pressurized coolant to transfer heat away from a certain area, then uses a high-powered fan to blow the resulting cold air where it's desired. A solar-powered fan, by contrast, merely blows hot air out of the car through its exhaust vent, and sucks presumably cooler air into the car through its intake vent [source: Chen]. Be careful while you're out on the road, though: It's not advisable to keep a solar ventilator mounted while you're actually driving, as the fan and solar panel assembly could block your vision out of either side window.

We've talked long enough about the doom-and-gloom side of things. What are the strengths of these devices? To learn about the benefits of solar-powered vehicle ventilators, go to the next page.